Long-Term Marijuana Use Changes Brain's Reward Circuit

Chronic marijuana use disrupts the brain’s natural reward processes, according to researchers at the Center for BrainHealth at The University of Texas at Dallas.

In a paper published in Human Brain Mapping, researchers demonstrated for the first time with functional magnetic resonance imaging that long-term marijuana users had more brain activity in the mesocorticolimbic-reward system when presented with cannabis cues than with natural reward cues.

Study participants rated their urge to use marijuana after looking at various visual cannabis cues, such as a pipe, bong, joint or blunt, and self-selected images of preferred fruit, such as a banana, an apple, grapes or an orange.

Researchers also collected self-reports from study participants to measure problems associated with marijuana use. On average, marijuana participants had used the drug for 12 years.

When presented with marijuana cues compared to fruit, marijuana users showed enhanced response in the brain regions associated with reward, such as the orbitofrontal cortex, striatum, anterior cingulate gyrus, precuneus and the ventral tegmental area.

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